Magnetrons require a strong and nearly uniform external magnetic field within the interaction region between the cathode and anode structures. Various magnetic-field generator solutions meet these requirements. One solution includes two “Helmholtz-like” coils or a solenoid, which can generate a nearly uniform field in a central region between the coils containing the magnetron. A second solution includes a “U-shaped” bar of iron with a coil at the bottom of the “U” and the magnetron placed between ends of the “U.” A third solution applies to a low-power magnetron, where external “U-shaped” permanent magnets are used. The permanent magnets according to the third solution are relatively large and heavy because a large amount of magnetic material is necessary to create the “U-shaped” permanent magnets. Specifically, the magnetron cathode and anode (the main magnetron structures) are very small, so the permanent magnets are located external to these main magnetron structures. The permanent magnets must be relatively large and heavy in order to generate the required magnetic field in the small interior region between the cathode and anode because the permanent magnets are located at some distance from the primary electron-beam interaction region in the gap between the cathode and anode.
Both of the magnetic-field generator techniques described above that use coils to generate the magnetic field required for high-powered magnetrons are large and heavy and require an external power source for the coils. The volume and weight associated with the power source adds additional size and weight to the magnetic-field generator/magnetron system. High-power magnetrons that have a high duty factor operation may require a method of cooling the magnet coils. A cooling system for the magnet coil adds additional size and weight to the magnetron. Many potential applications for a magnetron cannot tolerate the weight or size of these magnetic-field generator techniques.